1. Field of the Invention
The present invention relates to an ink jet printing apparatus and a control method thereof. In particular, the invention relates to an ink jet printing apparatus which can prevent unnecessary jetting of ink droplets and a control method thereof.
2. Background of the Invention
An on-demand ink jet printing apparatus is known which forms an image on a recording sheet by jetting ink droplets from nozzles arranged on a print head.
When this on-demand ink jet printing apparatus performs printing by interleave scanning, for instance, unnecessary jetting of ink droplets by inputting, in scanning the outside of a printing area, printing data indicating prohibition of jetting to a head driving circuit. However, in this on-demand ink jet printing apparatus, the quality of a printed image is not good because it is formed according to presence/absence (two values) of ink dots.
On the other hand, the present assignee has improved the quality of a printed image by providing a two-liquid-mixing type ink jet printer (hereinafter referred to as xe2x80x9ccarrier jet printerxe2x80x9d) which can perform halftone printing by jetting a mixture of ink and a dilution liquid from nozzles.
However, in the above carrier jet printer, a transparent dilution liquid is jetted even when the printing data is xe2x80x9c00,xe2x80x9d i.e., blank data, possibly soiling a recording sheet by forming a stain etc. Therefore, a means for preventing unnecessary jetting in the outside of a printing area is desired.
It is therefore an object of the present invention to provide an ink jet printing apparatus which resolves the above-mentioned problem.
It is another object of the invention to provide an ink jet printing apparatus control method which resolves the above-mentioned problem.
According to the invention, there is provided an ink jet printing apparatus including a print head and control means. The print head is moved with respect to a recording medium in the main scanning direction. The print head has N ink jetting portions arranged in an auxiliary scanning direction which is perpendicular to the main scanning direction. The N ink jetting portions are arranged at intervals that are K times the resolution element interval, where the ratio K/N is a fraction in lowest terms. The control means controls operations of the N ink jetting portions for each scan of the print head in the main scanning direction as the print head is scanned with respect to the recording medium in the main scanning direction and/or the auxiliary scanning direction.
According to the invention, there is provided a control method of an ink jet printing apparatus. The ink jet printing apparatus includes a print head which is moved with respect to a recording medium in the main scanning direction. The print head has N ink jetting portions arranged in an auxiliary scanning direction which is perpendicular to the main scanning direction. The N ink jetting portions are arranged at intervals that are K times the resolution element interval, where the ratio K/N is a fraction in lowest terms. The control method includes the steps of scanning the print head with respect to the recording medium in the main scanning direction and/or the auxiliary scanning direction, and controlling operations of the N ink jetting portions for each scan of the print head in the main scanning direction.